This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application entitled HEATER OF BUBBLE-JET TYPE INK-JET PRINTHEAD ENABLING GRAY SCALE AND MANUFACTURING METHOD THEREOF filed with the Korean Industrial Property Office on Jul. 24, 2000 and there duly assigned Serial No. 42366/2000.
1. Field of the Invention
The present invention relates to a heater of a bubble-jet type ink jet printhead, and more particularly, to a heater of a bubble-jet type ink jet printhead for gray scale printing and a manufacturing method thereof.
2. Description of the Related Art
The ink ejection mechanisms of an ink-jet printer are largely categorized into two types: an electro-thermal transducer type (or bubble-jet type) in which a heater consisting of resistive heating elements is used to produce a bubble in ink causing ink drops to be ejected, and an electro-mechanical transducer type in which a piezoelectric crystal bends to change the volume of ink causing ink drops to be ejected. Accomplishing a gray scale, that is, the series of achromatic shades, is one of the major functions of an ink jet printer. Typically, to effect gray scale printing, the volume of ink ejected, i.e., the size of ink droplets is adjusted to affect the size of dots represented on a print sheet.
It is known that a bubble-jet type ink jet printhead has difficulties in accomplishing gray scale printing while it is advantageous over an electro-mechanical transducer in high volume production. Thus, it is highly desirable to have a bubble-jet type ink jet printhead for effecting gray scale printing. What is needed is a design for a bubble-jet type ink jet print head that is easy to manufacture and that can easily produce varying shades of gray by energizing specific ones or a plurality of heaters for each nozzle hole producing ink droplets of varying sizes depending on what combination of heaters are energized.
To solve the above problems, it is an objective of the present invention to provide a heater and electrode arrangement for a bubble-jet type ink jet printhead adapted to produce gray scale printing more quickly and easily.
It is another objective of the present invention to provide a method of manufacturing the heater.
It is yet another object of the present invention to provide a plurality of heaters for each nozzle hole, allowing one, some, or all of the heaters to be energized during a printing process producing ink droplets of varying sizes depending on which heater or what combination of heaters are energized, resulting in the capability to produce varying shades of gray on a recording medium.
It is still an object of the present invention to be able to provide a variety of bubble-jet type ink jet printhead structures that can accommodate the plurality of heaters for each nozzle hole.
It is further an object of the present invention to provide various locations wherein the plurality of heaters and the corresponding plurality of electrodes can be located for a given bubble-jet type ink jet printhead structure.
It is still yet another object of the present invention to provide a simple and easy method of manufacture of the heater/electrode structure and the bubble-jet type ink jet printhead structure as disclosed in this invention.
Accordingly, to achieve the above objectives, the present invention provides a heater of a bubble-jet type ink jet printhead for enabling gray scale. The heater includes two or more heating elements arranged concentrically around a nozzle. Each of the heating elements is formed in polygonal or circular shape and spaced apart by a different distance from the center of the nozzle. Each heating element is coupled to an electrode for applying heater drive power independently.
Thus, heater drive power is applied to each electrode selectively or in combination to form bubbles having different volumes, thereby ejecting ink droplets in different sizes to effect gray scale printing. Furthermore, gray scale printing is accomplished with one-time application of heater drive power to enable high-speed printing, and thus there is no problem with increasing a drive cycle.
The present invention provides a method of manufacturing a heater according to the invention including the steps of a method of manufacturing a heater of a bubble-jet type ink jet printhead including the steps of: forming a first heating element in the shape of polygonal or circle having a predetermined diameter on a substrate; forming a first electrode for applying heater drive power to the first heating element; forming a second heating element in a circular shape having a diameter larger than that of the first heating element concentrically with the first heating element, or in a polygonal shape; and forming a second electrode for applying heater drive power to the second heating element.
Here, an insulating layer may be interposed between the first heating element and the first electrode and the second heating element and the second electrode thereby electrically insulating them from each other. The first and second heating elements may be formed of the same material thereby electrically connecting to each other. Accordingly, the present invention can provide a heater which simply enables gray scale by applying a typical heater manufacturing method.